<?php
/*
 *  $Id$
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.doctrine-project.org>.
 */

namespace Doctrine\Common;

use Doctrine\Common\Events\Event;

/**
 * The EventManager is the central point of Doctrine's event listener system.
 * Listeners are registered on the manager and events are dispatched through the
 * manager.
 * 
 * @license http://www.opensource.org/licenses/lgpl-license.php LGPL
 * @link    www.doctrine-project.org
 * @since   2.0
 * @version $Revision: 3938 $
 * @author  Guilherme Blanco <guilhermeblanco@hotmail.com>
 * @author  Jonathan Wage <jonwage@gmail.com>
 * @author  Roman Borschel <roman@code-factory.org>
 */
class EventManager {
	/**
	 * Map of registered listeners.
	 * <event> => <listeners> 
	 *
	 * @var array
	 */
	private $_listeners = array();
	
	/**
	 * Dispatches an event to all registered listeners.
	 *
	 * @param string $eventName The name of the event to dispatch. The name of the event is
	 * the name of the method that is invoked on listeners.
	 * @param EventArgs $eventArgs The event arguments to pass to the event handlers/listeners.
	 * If not supplied, the single empty EventArgs instance is used.
	 * @return boolean
	 */
	public function dispatchEvent($eventName, EventArgs $eventArgs = null) {
		if( isset( $this->_listeners[$eventName] ) ) {
			$eventArgs = $eventArgs === null ? EventArgs::getEmptyInstance() : $eventArgs;
			
			foreach( $this->_listeners[$eventName] as $listener ) {
				$listener->$eventName( $eventArgs );
			}
		}
	}
	
	/**
	 * Gets the listeners of a specific event or all listeners.
	 *
	 * @param string $event The name of the event.
	 * @return array The event listeners for the specified event, or all event listeners.
	 */
	public function getListeners($event = null) {
		return $event ? $this->_listeners[$event] : $this->_listeners;
	}
	
	/**
	 * Checks whether an event has any registered listeners.
	 *
	 * @param string $event
	 * @return boolean TRUE if the specified event has any listeners, FALSE otherwise.
	 */
	public function hasListeners($event) {
		return isset( $this->_listeners[$event] ) && $this->_listeners[$event];
	}
	
	/**
	 * Adds an event listener that listens on the specified events.
	 *
	 * @param string|array $events The event(s) to listen on.
	 * @param object $listener The listener object.
	 */
	public function addEventListener($events, $listener) {
		// Picks the hash code related to that listener
		$hash = spl_object_hash( $listener );
		
		foreach( ( array ) $events as $event ) {
			// Overrides listener if a previous one was associated already
			// Prevents duplicate listeners on same event (same instance only)
			$this->_listeners[$event][$hash] = $listener;
		}
	}
	
	/**
	 * Removes an event listener from the specified events.
	 *
	 * @param string|array $events
	 * @param object $listener
	 */
	public function removeEventListener($events, $listener) {
		// Picks the hash code related to that listener
		$hash = spl_object_hash( $listener );
		
		foreach( ( array ) $events as $event ) {
			// Check if actually have this listener associated
			if( isset( $this->_listeners[$event][$hash] ) ) {
				unset( $this->_listeners[$event][$hash] );
			}
		}
	}
	
	/**
	 * Adds an EventSubscriber. The subscriber is asked for all the events he is
	 * interested in and added as a listener for these events.
	 * 
	 * @param Doctrine\Common\EventSubscriber $subscriber The subscriber.
	 */
	public function addEventSubscriber(EventSubscriber $subscriber) {
		$this->addEventListener( $subscriber->getSubscribedEvents(), $subscriber );
	}
}